Polyethylene terephthalate filament yarns, as well as other fibrous materials, are sometimes subjected to a series of thermomechanical treatments, such as false twist texturizing, subsequent to spinning and prior to or concurrently with dyeing to obtain a property-balance dictated by the end use of the fibrous material.
It has been an observed characteristic of crystalline fibrous materials such as those prepared from polyethylene terephthalate that dye uptake is a function of fiber structure (e.g., degree of crystallinity and orientation) and slight changes in fiber structure will induce variations in the dye uptake (i.e., the ratio of weight of the dye to the weight of the fabric containing the dye).
It is also a generally observed characteristic of crystalline fibrous materials such as polyethylene terephthalate that false twist texturizing treatments of fibrous materials as described herein will induce changes in the fiber structure.
Furthermore, it is well known that, due to inherent design limitations in the heating equipment employed in such false twist texturizing treatments, it is virtually impossible to subject all of the fibrous material which is essentially incorporated into a final end product to a uniform temperature during any particular treatment. The temperature of any false twist texturizing treatment can therefore be characterized as inherently being a range of temperatures.
Consequently, the inherent variation in temperature to which a fibrous material is subjected during false twist texturizing induces a variation in the structure of the fiber which in turn induces a variation in dye uptake. This variation in dye uptake results in an end product having a non-uniform appearance with respect to dyeshade.
Various methods of improving the dye affinity of fibrous materials are illustrated by U.S. Pat. Nos. 3,527,862; 3,558,761; 3,634,580 and 3,739,056.
Typical heat treatments which have been applied to fibrous materials are illustrated by U.S. Pat. Nos. 3,469,001; 3,471,608; 3,527,862; 3,546,329; 3,562,199; 3,562,382; 3,584,103 and 3,595,952.
A method for improving the uniformity of dye uptake is disclosed in U.S. Pat. No. 3,847,544.
None of the above mentioned patents is directed to improving the uniformity of dye uptake in the manner described hereinafter.
Thus, there has been a continuing search for ways to reduce the sensitivity of fibrous materials, such as polyethylene terephthalate, to variations in dye uptake induced by variations in the temperature to which they are subjected during typical false twisting procedures.
The present invention is a result of this search.
It is therefore an object of the present invention to provide a process for enhancing the uniformity of dye uptake of a previously oriented fibrous material comprising a substantial proportion of polyethylene terephthalate which is subjected to a false twist texturizing treatment prior to or concurrently with dyeing.
These and other objects as well as the scope, nature, and utilization of the claimed invention will be apparent from the following detailed description and appended claims.